According to my friend who manages a hobby shop, the kit number means the T-55 is...yes!...all new! He is eagerly anticipating it too, since he's a big armor fan.
A funny thing: I live near 2 fairly large hobby shops who do international mail order. Neither had heard about this TAMIYA T-55 kit yet. My friend checked with his regional distributor. They didn't know about it, either.
Don't you love the Internet? We heard it first here!
My friend showed me a list of TRUMPETER kits that will be coming out under the MINI-HOBBY brand name. This seemed to be all old (and mostly bad) stuff, like the infamous M-60A1 and the LVTP-7's.
BTW, he also had some photos of the TRUMPETER Swedish S-Tank sprues, taken at the Chicago hobby show. It looks great!